The present invention relates to a valve arrangement, which is attached to the mouth tap of a pressure vessel containing compressed gas such as nitrogen or carbon dioxide, and is capable of charging and discharging such compressed gas.
A conventional valve arrangement of this kind comprises, as shown in FIG. 17, a valve body B sealed to a mouth tap A of a pressure vessel, a large-diameter valve operating bore C which is formed on said valve body B and which communicates with the inside of said pressure vessel, a small-diameter nozzle hole D formed on said valve body B which communicates said valve operating bore C with the outside, a valve member F which is seated on the inner-most valve seat E of said valve operating bore C, and which closes said nozzle hole D, a plunger G which protrudes from the end of said nozzle hole D and is capable of sliding into said nozzle hole D which is attached to said valve member F, and a pressure-exerting spring H fitted within said valve operating bore C to apply constant pressure upon said valve member F so that it will always sit on said valve seat E.
In conventional valve arrangements constructed as described above, unless the gap between the plunger G and the nozzle hole D is small, the valve member F will wobble, preventing it from being firmly seated on the valve seat E and thus preventing tight sealing.
On the other hand, a small gap between the plunger G and the nozzle hole D reduces the efficiency of gas charging since the gas flows through said gap, causing the gas charging operation to take a longer time.
Furthermore, if the pressure at the consuming side exceeds that in the pressure vessel, the valve member F will open against the pressure caused by the pressure-exerting spring H. It will allow the gas's back-flow, causing liquids and the like other than gas, to be introduced into the pressure vessel.